OVER 5K LOGITECH S/Ns

I've already leeched 3 things today so I'll come back to this tomorrow. (Just a meme, not a leecher no ban <3)

How does Social Engineering work? I've been trying to understand it but are there any examples/tutorial videos that I could follow? Not sure exactly what to say do or any of that. I know I can go on craigslist and ask a seller for their items serial number to "verify" it's real but just steal it but that's all I know.